| Western Yellowjacket - Vespula pensylvanica [1] Live adult yellowjacket wasps photographed at Arkansas River near Buena Vista, Chaffee County, Colorado, USA Size: 15mm. [Bees & Wasps of North America Table of Contents] [Bees & Wasps of North America Main Page Graphics] |
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Yellowjackets are considered quite beneficial to agriculture since they feed abundantly on harmful flies and caterpillars, but they become a nuisance when they scavenge for food at picnics or other outdoor venues where food or sugary beverages are served. Many are attracted in large numbers to garbage cans, others fly in and out of nests built around homes, buildings and areas where people live. One simple way to avoid attracting yellowjacks and wasps to your picnic is to serve only "diet" beverages, that is, those that don't contain sugar. These insects have no interest whatesoever in liquids that do not contain sugar. Should a yellowjacket wasp fly near you or land on your body, never swing or strike at it or run rapidly away since quick movements often provoke a sting. When a wasp is near you, it's best to do the same as the wasp: it is ignoring you, and you should it. Most stings are provoked by persons swatting at or otherwise harassing insects which really have no knowledge of your existence until so provoked.
My dad once asked me to eradicate a nest right next to his back door, and I very reluctantly agreed. The wasps were entering and leaving their underground nest via a hole in a railroad tie landscape timber. Well, kids, this turned out to be a gigantic nest of wasps, despite it modest entrance! A can of Raid flying insect spray later, my dad and I had both been stung mutiple times, and those yellowjacket were VERY riled up, defending their nest. Yellowjackets don't have barbs on their stingers like honeybees. They'll grab onto your clothing and just keep stinging you until you get the picture and swat them to the ground - and it takes a healthy swat, too. The stings were very painful, and itched and burned for days afterwards. As it is, I consider these little stinging machines to be beautiful and fascinating creatures: wonders of nature outside your backdoor.
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Yellowjackets are social wasps living in colonies containing workers, queens and males. Colonies are annual with only inseminated queens overwintering. Fertilized queens occur in protected places as hollow logs, in stumps, under bark, in leaf litter, in soil cavities and human-made structures. Queens emerge during the warm days of late April or early May, select a nest site and build a small paper nest in which eggs are laid. After eggs hatch from the 30 to 50 brood cells, the queen feeds the young larvae for about 18 to 20 days. Larvae pupate, emerging later as small, infertile females called workers. By mid-June, the first adult workers emerge and assume the tasks of nest expansion, foraging for food, care of the queen and larvae, and colony defense. From this time until her death in the autumn, the queen remains inside the nest laying eggs. The colony then expands rapidly reaching a maximum size of 4,000 to 5,000 workers and a nest of 10,000 to 15,000 cells in August and late September. At peak size, reproductive cells are built with new males and queens produced. Adult reproductives remain in the nest fed by the workers. New queens build up fat reserves to overwinter. Adult reproductives leave the parent colony to mate. After mating, males quickly die while fertilized queens seek protected places to overwinter. Parent colony workers dwindle, usually leaving the nest and die, as does the foundress queen. Abandoned nests rapidly decompose and disintegrate during the winter. Nests inside structures will persist as long as they are dry. Nests are not used again. In the spring, the cycle is repeated. (Weather in the spring is the most important factor in colony establishment.) Although adults feed primarily on items rich in sugars and carbohydrates (fruits, flower nectar and tree sap), the larvae feed on proteins (insects, meats, fish, etc.). Adult workers chew and condition the meat fed to the larvae. Larvae in return secrete a sugary material relished by the adults. (This exchange of material is known as trophallaxis.) In late autumn, foraging workers (nuisance scavengers) change their food preference from meats to ripe, decaying fruits since larvae in the nest fail to meet requirements as a source of sugar. |
Compare to: Downy Yellowjacket - Vespula flavopilosa
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 Paper Wasp Polistes dominula |  Tricolored Bumble Bee Bombus ternarius |  Cuckoo Bee Nomada sp. |  Bald-faced Hornet Dolichovespula maculata |